The present invention relates to a method of producing a two-layered copper-clad laminate in which a copper layer is formed on a polyimide film through sputtering and plate processing and the folding endurance of the laminate is improved, as well as to a two-layered copper-clad laminate obtained from the foregoing method.
Incidentally, the foregoing two-layered copper-clad laminate covers cases of forming a thin interlayer in order to increase the bond strength, and this is collectively referred to as a “two-layered copper-clad laminate” of a polyimide film and a copper layer.
Recently, two-layered copper-clad laminate (CCL: Cu Clad Laminate) material in which a copper layer is formed on a polyimide film has been used as circuit material in driver IC for liquid crystal display and other devices, for which fine pitch circuits are required. Among the two-layered CCL materials used as laminate materials for COF (Chip On Film), attention is particularly focused on the two-layered CCL material manufactured by sputtering and plate processing.
The two-layered CCL material is produced by forming a copper layer with a submicron-level thickness on a polyimide film (PI) through sputtering and then forming a copper layer through copper-sulfate plating. The basic invention is described in Patent Document 1 indicated below.
A COF (Chip On Film) is used in flat-panel televisions such as LCD televisions and organic EL televisions, and since the outer lead part of the circuit is used by being folded, the folding endurance needs to be high.
Nevertheless, the circuit line width became narrow due to the advancement in finer pitches of circuits, and a problem arose in that the strength deteriorated. Consequently, a problem arose in that a disconnection of the outer lead part would occur.
[Patent Document 1] U.S. Pat. No. 5,685,970